1. Field of the Invention
The present invention relates to a starter for starting an engine.
2. Description of the Prior Art
FIG. 14 is a sectional view showing one example of a conventional starter that was disclosed in Japanese Published Unexamined Patent Application No. 266933/1998.
In FIG. 14, 1A is an output shaft. An electromagnetic switch 2A, an over-running clutch 30A provided with a pinion 30P which meshes with a ring gear 50A, a plunger 40A comprising an inner plunger 4A and an outer plunger 4B are arranged on the same shaft as the output shaft 1A. A starter with this structure is generally called a coaxial type starter.
12A is an armature of a DC motor and 16A is a shaft (a motor shaft). 18A is a reduction mechanism which reduces the rotational force of the shaft 16A and transmits it to the output shaft 1A.
8A is a contact shaft supported by an inner gear 17A of the reduction mechanism 18A almost parallel with the plunger 40A through a supporting hole 17m.
100 is a bracket and 800 is a shift plate which connects the plunger outer 4B with the contact shaft 8A.
Further, the upper side from the center axis in FIG. 14 shows the state of a starter not in operation and the lower side shows the state wherein the starter is in operation with an electromagnetic switch turned ON and the pinion meshed with the ring gear.
Next, the operation of the starter is explained.
First, when an ignition switch is turned ON and current flows to an exciting coil 2B of the electromagnetic switch 2A, the outer plunger 4B is attracted by an exciting core 2C of the electromagnetic switch 2A. This conventional starter has such a structure that the outer plunger 4B is directly connected with the contact shaft 8A via the shift plate 800 and when the outer plunger 4B is attracted by the exciting coil 2B, the contact shaft 8A is also moved simultaneously. Between the outer plunger 4B and the inner plunger 4A, there is a coil spring 401 mounted on a spring bracket 400 and the inner plunger 4A is kept in the stationary state because the coil spring 401 deflects at the initial stage even when the outer plunger 4B is attracted and begins to move. In front of the inner plunger 4A, an inner clutch 30B is mounted via a shifter member 402 and as long as the inner plunger 4A is kept in the stationary state, the inner clutch 30B is also kept in the stationary state. After a short interval when the plunger 4B is attracted and begins to move, a movable contact 80A mounted on the contact shaft 8A comes into contact with a stationary contact 80B mounted in a contact chamber ZA. When the movable contact 80A is brought into contact with the stationary contact 80B, electric power is supplied from an external power source via a contact bolt 11A, and an armature 12A begins to turn. When the output shaft 1A begins to turn by way of the reduction mechanism 18A, the pinion 30P is caused to move toward the ring gear 50A by a thrust generated in a helical spline portion 1B, and the threads and the thread grooves of the pinion 30P and the ring gear 50A agree and mesh. Thereafter, when the engine starts, the output shaft 1A and the pinion 30P are separated by the action of the overrunning clutch 30A and the pinion 30P runs idle. When the power supply to the exciting coil 2B is stopped, the pinion 30P is disengaged from the ring gear 50A by return springs 403, 404.
However, in the case of a conventional starter disclosed in Japanese Published Unexamined Patent Application No. 266933/1998, there have been problems whereby a pigtail 42 (a lead wire) for electrical connection with a brush 43 is connected to the movable contact 80A and whenever the contacts 80A, 80B are opened/closed, a repetitive stress is applied to the pigtail 42. Also, worn powder from the brush 43 enters the contact chamber ZA because this chamber is not airtight.
Further, in the case of a conventional starter disclosed in Japanese Published Unexamined Patent Application No. 319926/1996 shown in FIG. 15, a contact chamber cover 45 is provided but a repetitive stress is applied to the pigtail 42 of the brush 43 similar to the case of the starter disclosed in Japanese Published Unexamined Patent Application No. 266933/1998 as the pigtail 42 is connected to the movable contact 80A. Further, in the conventional technology shown in this FIG. 15, the contact chamber ZA is covered by the contact chamber cover 45 but under this contact chamber cover 45, a space is formed for the movable contact 80A to move and the contact chamber ZA is not kept in an airtight state. Therefore, there has been a problem whereby worn powder from the brush enters the contact chamber ZA in the same manner as with the starter shown in FIG. 14.